With an increase in a data rate in a mobile communication system, the radio frequency tends to be increased and the size of cells tends to be reduced. In addition, the size of cells is limited in some cases due to geographical constraints or building constraints.
A distributed antenna system, for example, has been proposed for such cases. The distributed antenna system includes remote access units as wireless processing sections each having an antenna and part of the base station functions. The remote access units are typically individually arranged in small cells. The small cells each arranged with the remote access units are regarded as one large cell in the distributed antenna system. The remote access units wirelessly communicate with terminal equipment (user equipment). In the distributed antenna system, a single base station may be used for various areas, and the number of times of handover may be reduced. Thus, the distributed antenna system may provide improved cost performance.
As a link topology (physical topology), a bus topology, a star topology or a hybrid topology that includes a bus topology and a star topology, is used.
As related techniques, the following techniques are known: a technique using various connection topologies; a technique using a loop topology; and a technique in which a base station transmits different multiple downlink signals so that multiple remote access units receive the signals, respectively.